fix(tui): avoid duplicate live reasoning summaries (#15758)

## TL;DR

Fix duplicated reasoning summaries in `tui_app_server`.

<img width="1716" height="912" alt="image"
src="https://github.com/user-attachments/assets/6362f25a-ab1c-4a01-bf10-b5616c9428c2"
/>

During live turns, reasoning text is already rendered incrementally from
`ReasoningSummaryTextDelta`. When the same reasoning item later arrives
via `ItemCompleted`, we should only finalize the reasoning block, not
render the same summary again.

## What changed

- only replay rendered reasoning summaries from completed
`ThreadItem::Reasoning` items
- kept live completed reasoning items as finalize-only
- added a regression test covering the live streaming + completion path

## Why

Without this, the first reasoning summary often appears twice in the
transcript when `model_reasoning_summary = "detailed"` and
`features.tui_app_server = true`.

codex-rs/tui_app_server/src/chatwidget.rs

@@ -5675,13 +5675,15 @@ impl ChatWidget {
             ThreadItem::Reasoning {
                 summary, content, ..
             } => {
-                for delta in summary {
-                    self.on_agent_reasoning_delta(delta);
-                }
-                if self.config.show_raw_agent_reasoning {
-                    for delta in content {
+                if from_replay {
+                    for delta in summary {
                         self.on_agent_reasoning_delta(delta);
                     }
+                    if self.config.show_raw_agent_reasoning {
+                        for delta in content {
+                            self.on_agent_reasoning_delta(delta);
+                        }
+                    }
                 }
                 self.on_agent_reasoning_final();
             }

codex-rs/tui_app_server/src/chatwidget/tests.rs

@@ -47,6 +47,7 @@ use codex_app_server_protocol::PluginMarketplaceEntry;
 use codex_app_server_protocol::PluginReadResponse;
 use codex_app_server_protocol::PluginSource;
 use codex_app_server_protocol::PluginSummary;
+use codex_app_server_protocol::ReasoningSummaryTextDeltaNotification;
 use codex_app_server_protocol::ServerNotification;
 use codex_app_server_protocol::SkillSummary;
 use codex_app_server_protocol::ThreadClosedNotification;
@@ -5135,6 +5136,56 @@ async fn replayed_reasoning_item_shows_raw_reasoning_when_enabled() {
     assert!(rendered.contains("Raw reasoning"));
 }
 
+#[tokio::test]
+async fn live_reasoning_summary_is_not_rendered_twice_when_item_completes() {
+    let (mut chat, mut rx, _op_rx) = make_chatwidget_manual(None).await;
+    chat.show_welcome_banner = false;
+
+    chat.handle_server_notification(
+        ServerNotification::TurnStarted(TurnStartedNotification {
+            thread_id: "thread-1".to_string(),
+            turn: AppServerTurn {
+                id: "turn-1".to_string(),
+                items: Vec::new(),
+                status: AppServerTurnStatus::InProgress,
+                error: None,
+            },
+        }),
+        None,
+    );
+    let _ = drain_insert_history(&mut rx);
+
+    chat.handle_server_notification(
+        ServerNotification::ReasoningSummaryTextDelta(ReasoningSummaryTextDeltaNotification {
+            thread_id: "thread-1".to_string(),
+            turn_id: "turn-1".to_string(),
+            item_id: "reasoning-1".to_string(),
+            delta: "Summary only".to_string(),
+            summary_index: 0,
+        }),
+        None,
+    );
+
+    chat.handle_server_notification(
+        ServerNotification::ItemCompleted(ItemCompletedNotification {
+            thread_id: "thread-1".to_string(),
+            turn_id: "turn-1".to_string(),
+            item: AppServerThreadItem::Reasoning {
+                id: "reasoning-1".to_string(),
+                summary: vec!["Summary only".to_string()],
+                content: Vec::new(),
+            },
+        }),
+        None,
+    );
+
+    let rendered = match rx.try_recv() {
+        Ok(AppEvent::InsertHistoryCell(cell)) => lines_to_single_string(&cell.transcript_lines(80)),
+        other => panic!("expected InsertHistoryCell, got {other:?}"),
+    };
+    assert_eq!(rendered.matches("Summary only").count(), 1);
+}
+
 #[test]
 fn rendered_user_message_event_from_inputs_matches_flattened_user_message_shape() {
     let local_image = PathBuf::from("/tmp/local.png");